Polyethercarbonate (PEC) polyols are known in the art. PEC polyols are utilized, in conjunction with a cross-linking agent, such as an isocyanate, to produce polyurethane polymers. The polyurethane polymers can be foamed or non-foamed, i.e., elastomeric. Generally, PEC polyols are the polymerization reaction product of an H-functional initiator, an alkylene oxide, and CO2 and these reactants are reacted in a reactor in the presence of a catalyst. More specifically, the PEC polyols are formed as a result of copolymerization of the alkylene oxides and CO2. Recently, there has been a significant focus on using catalysts that include a multimetal cyanide compound to catalyze the reaction of the H-functional initiator, the alkylene oxide, and CO2 to form the PEC polyols.
Although the recent focus has been to use conventional multimetal cyanide compounds, such as Zn3[Co(CN)6]2, it has been observed that these conventional compounds are not well suited for catalyzing the copolymerization of alkylene oxide with CO2 to yield the PEC polyol. When using the conventional multimetal cyanide compound, the extent that the CO2 is incorporated into the PEC polyol, specifically into the desired alkylene oxide—CO2 copolymer, is limited and difficult to control. Conventional multimetal cyanide compounds can possess amorphous structures and it is believed that, in part, these properties of conventional multimetal cyanide compounds contribute to the overall lack of activity of the catalysts in the copolymerization of alkylene oxide with CO2. As a result of the above, high CO2 pressures and/or low process temperatures are required to generate PEC polyols with adequate CO2 content. It is known that high CO2 pressures are undesirable due to the high cost of high pressure equipment and low process temperatures are undesirable due to the high catalyst (multimetal cyanide compound) concentrations and/or long cycle times required when low process temperatures are employed. Additionally, when using the conventional multimetal cyanide compound to form the PEC polyol, formation of cyclic alkylene carbonate as an undesirable byproduct of the copolymerization of the alkylene oxide and CO2 is considerable.
Instead of being used to form PEC polyols, it is known that conventional multimetal cyanide compounds are more suited for the homopolymerization of alkylene oxide to form a polyether polyol. Multimetal cyanide compounds have ordered structures that are defined by cationic catalytic centers and anionic backbones. The anionic backbones are spatially arranged about the cationic catalytic centers and these cationic catalytic centers of the multimetal cyanide compounds are ideally spaced to promote the homopolymerization of alkylene oxides to form the polyether polyol. Due to this ideal spacing, it is contemplated that the conventional multimetal cyanide compounds are essentially too active for the homopolymerization of alkylene oxide and, therefore, the growing carbonate chain ends in the PEC polyol are biased toward polymerization with alkylene oxide rather than CO2.
In view of the limitations associated with conventional multimetal cyanide compounds when used to form PEC polyols, including those limitations described above, there remains an opportunity to modify these multimetal cyanide compounds such that the compounds are more suitable for use in the formation of the PEC polyol. There also remains an opportunity to avoid use of the conventional multimetal cyanide compounds, which inherently have ideal spatial arrangements, altogether.